Eclipses' effect on wind revealed

March 29, 2012
by Tom Marshall

Solar eclipses don't just turn the lights out; they also make the wind slow down and change direction.

Scientists compared hourly measurements of wind speed and direction from 121 weather stations across southern England during the August 1999 total solar eclipse with the output of a high-resolution weather forecast model that wasn't programmed to represent the eclipse.

The model agreed very closely with the instruments' readings right up until the eclipse began. It then showed what the weather would have been like if the eclipse hadn't happened, giving researchers a much more accurate idea of its effects.

'The eclipse was like a giant natural experiment,' says Dr Suzanne Gray of the University of Reading, lead author of the paper in Proceedings of the Royal Society A. The study shows that scientists can now use high-resolution weather models to look at local weather changes of small magnitude, like those caused by solar eclipses.

The results show that average wind speed across an inland cloud-free region over southern England dropped by 0.7 metres per second, and that the wind's direction turned anticlockwise by an average of 17°  effectively, the eclipse was causing the winds to become more easterly. Temperatures also fell by an average of about 1°C.

Previous work on the subject has been based only on measurements in a few places, rather than from a network as in this case. And it didn't compare these measurements with a weather model to predict what would have happened without the eclipse.

It's only recently become possible to do this kind of experiment, after huge improvement in high-resolution weather forecast models over the last decade. 'We could never have done this when the eclipse occurred,' says Gray, 'but now we can use the model to get a far better idea of its impact on the wind.'

Temperatures are likely to fall when the Earth is deprived of sunlight, just like they do at night. And the slower wind speeds weren't unexpected, Gray says - cooling the atmosphere close to the ground removes energy from it, damping turbulence, which will probably mean less wind. But the changes in wind direction were more of a surprise.

The effects were so pronounced that they can be seen even in measurements that are taken hourly, which is very infrequent in the context of such a transient event as an eclipse.

The results seem to fit the 'eclipse cyclone' hypothesis proposed in 1901 by H Helm Clayton, one of the first scientists to investigate eclipses' impact on the weather. He suggested that when the moon's gigantic shadow falls on the Earth, it causes a core of cold air around which a weak, short-lived cyclone forms, skewing the winds anticlockwise.

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10 comments

I thought that when the sunlight is blocked the winds driven by them would slow down and that when the wind speeds up it veers and backs when it slows down. i.e. it does what you'd expect. Presumably it does the opposite in the southern hemisphere?

What is interesting though is that in the coldest parts of the solar system the winds are the strongest, showing that sunlight isn't everything.

IMO so called the Allais effect is of the same origin, it just increases the density of atmosphere of neutrinos around Earth when the gravitational shield of massive objects hits the surface of Earth. Because this atmosphere is sparse but huge, it leads into significant gravitational anomaly. IMO the various whole moon effects could have the same origin: the increased density of neutrinos influences the human psychic, because the human brain relies on collective motion of charged particles. In this connection this recent effect may be quite interesting 1, 2. Maybe the astrologers were right, when they connected the eclipses and planetary conjunctions with increased frequency of wars and disasters.

"IMO the various whole moon effects could have the same origin: the increased density of neutrinos influences the human psychic, because the human brain relies on collective motion of charged particles."

In this case I trust your views on the origin of lunacy. You repeatedly demonstrate you have the inside track here when it comes to lunatic ideas; ie "Maybe astrologers were right...."?

What you trust in or not is not relevant - the important is, what you can prove or disprove

You want to prove something with: 1. BBC News on a ""research"" carried out by Sussex Police...2. A link to story where a Justice Minister (Annette King) blame the sun and the moon. But i like the fifth sentence: ""It almost beggars belief that someone with that level of experience could say something so ridiculous," Mr Power reportedly said."3. You really should read the links you provide: "conclusion: The plots show no convincing peak or sinusoidal variation in phase with either the lunar phases or varying distance due to the Moon's orbit."

Now, please, stop posting such crap. Or at least dont be suprised getting downvoted and reported for spamming crap.

A good place to perform a similar experiment is the Great Plains of the US. Every summer (actually late spring through early fall) cumulus clouds form in the early afternoon and drift across the sky with the prevailing winds. As the clouds pass overhead the changes in wind speed, direction and temperature are palpable. No solar eclipse required - only differential heating of the landscape.

The labelling the coincidence as a crap has nothing to do with scientific method. For example, the moon, month, and menstruation are all related etymologically. No less an authority than Charles Darwin believed that menstruation was linked to the moon's influence on tidal rhythms, that the moon's cycle of phases is 29.53 days, while the human female menstrual cycle averages 28 days, 28 days for opossums, 24 to 26 days for macaque monkeys, 37 days for chimpanzees 11 days for guinea pigs, 21 days for cows and mare, etc. The tendency of higher organisms to avoid interference with lunar cycles is apparent here. For example the biologist Winnifred Cutler, in a 1980 paper, found that 40 percent of women in a random sample showed "a preponderance of menses onsets in the light half-cycle of the month" (the two weeks centered on the full moon).

This study claimed that an unusual number of traffic accidents occurred during the evenings right around the full and new moons. There are dozens of similar studies, but formally thinking people refuse to admit every subliminal evidence.http://tra.sagepu...abstracthttp://www.ncbi.n.../9530753http://www.ncbi.n...16407788http://www.ncbi.n...18786384A new twist was recently given to lunar-effect theorizing by the discovery that positive and negative ions in the atmosphere have an effect on behavior (negative ions usually favorable, positives the opposite). It turns out that positive ions are more abundant when the moon is full.